1. Technical Field of the Invention
The invention concerns a method for producing brush ware comprising at least one carrier and bristles made from a moldable plastic material disposed thereon, wherein the bristles are produced from the plastic melt through injection into bristle-shaped molding channels. The invention also concerns a device for producing brush ware and brush ware.
2. Prior Art
Brush ware, in the present case in particular brushes of any kind, paint brushes and brooms, is manufactured mainly mechanically by initially producing the brush carrier with holes and then mechanically introducing the bristle bundles. With the use of plastic materials, the brush bodies have been produced by molding or injection and the bristles have been fastened either in a conventional mechanical fashion or more recently through thermal methods. In any case, the bristle monofilaments must be initially produced in an extrusion or spinning process, the monofilaments must be optionally cut and the bristles must be subsequently fastened to the carrier. With current conventional anchoring technology, the bristles are looped and punched into the brush body using a metallic anchor.
There have been many attempts to streamline the process by producing the bristles or bundles in one piece, together with the carrier, and connecting the carrier to the brush body. More than 100 years ago (GB 788/1861, GB 24 935/1896), one has proposed molding the bristles and a carrier, to which they are connected, using an elastic material such as rubber or the like and to subsequently mount them on an intrinsically rigid brush body. The production of cleaning elements, combined into groups, together with a carrier connecting same in one common injection process and the subsequent connection of the carrier to the brush body optionally in a two component injection method has also been suggested (DE 941 364, GB 2 151 971, U.S. Pat. Nos. 301,644, 4,244,076, 5,040,260, 5,966,771, WO 98/03097). Finally, U.S. Pat. No. 5,926,900 has suggested production of the entire brush body and the bristles as a one-piece, injection molded part.
Brushes of this type were only used in practice for hair care or—to a smaller extent—as throwaway brushes. These brushes are not suitable for many applications, since the bristles of such injection-molded brushes have an unacceptably low bending strength. In contrast to bristles produced in a spinning process, they do not have the molecular structure required for stability, which is mainly characterized by a longitudinal orientation of the molecular chains, in a bristle-parallel manner. For this reason, they must be primarily regarded as working or cleaning elements rather than bristles. The lack of stability is particularly noticeable in the region where the working elements are connected to the carrier, where orientation of the molecules is completely missing. In consequence thereof, the working elements, which are properly aligned directly after production, will change their positions after a short period of use and tend to bend, break and not to re-erect (bend recovery). This technology further requires use of the same plastic material for the working elements and the carrier. This leads to increased costs since high quality bristles must be produced from high-quality plastic materials. Every effort to reduce costs necessitates a compromise in the selection of the plastic material. Since the considerable disadvantages concerning use always remain, brushes of this type are suitable for few applications. A differentiation between the carrier material and that for the bristles or among the bristles in dependence on the respective requirements is not possible, in particular with regard to mechanical strength, coefficient of friction, color etc.
Brushes are also known (U.S. Pat. No. 2,621,639) having working elements (“pins”) which are not actual bristles rather pins, bolts, strips or the like. They are injection-molded elements, which consist mainly of rubber or rubber-elastic plastic materials, e.g. elastomers, and have a larger cross-section and frequently also a shorter length than bristles. This compact construction of the “bristle” in this type of brush is absolutely necessary for two reasons: to obtain satisfactory stability and fatigue strength and to prevent the molding channels from being too narrow and deep for an injection having sufficient mold filling as well as to permit removal. The characteristic properties of these “pins” are that they have a soft effect on the surface treated and an increased coefficient of friction, i.e. they effect a type of stroking and massaging and not an active brushing. A typical field of application is hairbrushes, which mainly serve for separating and arranging hair and are supposed to only massage the skin of the head. The rigidity of these elements can only be substantially influenced by the diameter and the diameter/length ratio as well as by the hardness of the plastic. The brush according to U.S. Pat. No. 2,621,639 is produced through injection molding by inserting a thin flexible carrier plate with a perforation into an injection mold in correspondence with the arrangement of the working elements, wherein the mold has a plurality of channel-like molding cavities which join the perforated holes of the carrier and serve to shape the pin-shaped working elements. The opposing side—the injection side—is provided with distributing channels which guide the plastic melt, e.g. nylon, to the individual perforated holes and into the adjacent molding channels. The molding channels are widened directly after the perforations of the carrier to produce a thickening on both sides of the thin carrier plate for axially fixing the working element in both directions. Although the nylon used would be suitable to achieve bristle-like properties, this is not utilized herein, since production of a longitudinal molecular structure is not possible, at least at the foot of the cleaning elements, due to the thickening. The same is true for another known hair brush (EP-B1-0 120 229) wherein a carrier is initially injected having sleeve-shaped conical protrusions and a further plastic material is then injected into the sleeves as a core which abuts the open sleeve end with a thickening. On the rear side, the cores are connected via a second carrier plate of the same material. This procedure is primarily intended to produce a positive, axially stable connection between both parts and makes the working elements bulkier.
Cleaning elements of this type are also known for toothbrushes and brooms (U.S. Pat. Nos. 5,040,260, 5,966,771). These brushes are formed in two parts. Finally, toothbrushes are known (U.S. Pat. Nos. 1,924,152, 2,139,242, DE 826 440, WO00/64307) wherein the bristle support consists of a combination of conventional bristles with proven, good cleaning effect and bolt or pin-like cleaning elements of rubber-elastic plastic material.